A text-book of sanitary and applied chemistry : or, The chemistry of water, air, and food

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Preface To First Edition

The object of this work is to furnish a textbook upon applied chemistry that is suitable for use by those students who have had a course in general chemistry, such as is usually completed in a good high school or in the earlier years of a college course. The particular phase of applied chemistry treated is that which pertains to the daily life of the household, but the subjects considered do not by any means cover the whole field of what might be called chemistry applied to daily life, but only the most important topics.

Although primarily intended for use as a textbook, much scattered material is here collected from Government Reports and elsewhere, so that it is believed the book will prove valuable for general information and reference. The difficulty of condensing, without sacrificing something in clearness, is thoroughly recognized.

Some simple reactions in general and organic chemistry have, it is true, been introduced, but it is believed that they are of a kind to be readily understood by students, with a little explanation from the instructor. It would be well to supplement the text by lectures on the topics studied and also to give time for discussions.

The author believes that a practical method for teaching the subject, if a sufficient number of books of reference are at hand, is to outline topically the subject to be studied and require a preparation on those topics from the student.

It has been the intention of the author to introduce enough facts to render the subject intelligible and readily

VI PREFACE TO FIRST EDITION

comprehended, and not to burden the pages with details which belong properly to a more voluminous treatise on the subject.

One of the most important features of the book is the introduction of experiments, which are distributed throughout the text and which it is believed will very materially aid the instructor who may have occasion to direct the work of the students. These experiments are suggested by several years of experience with classes in Sanitary and Applied Chemistry, and they are of such a character as can be performed in any chemical laboratory and with a moderate amount of inexpensive apparatus. More difficult experiments, which would involve a knowledge of quantitative analysis, have been purposely omitted. The instructor can add more experiments, if sufficient apparatus is at hand and the time allotted to the course will permit.

The first part of the book is devoted to water, air, heating, lighting, and ventilation, — to those practical problems with which we come in contact every day ; and the second part is occupied with a discussion of foods and beverages. In the latter section, although many adulterants are pointed out and the simpler tests for them are given in the experiments, no attempt is made to do the work, which properly belongs to the trained microscopist or analytic chemist.

For many valuable suggestions, which were made while the book was going through the press, and for assistance in reading proof, the author is especially indebted to Professor J. T. Willard, Dr. James Naismith, Professor Isabel Bevier, Professor M. A. Barber, Dr. H. P. Cady, Dr. W. D. Bigelow, Professor W. C. Hoad, and Mrs. A. T. Bailey.

Preface To The Fourth Edition

In preparing this edition the text has been corrected, much of it has been rewritten, and distinctive headlines have been added wherever it seemed that greater clearness could be attained. The chapters on Purification of Water Supplies and on Sewage Disposal have been brought down to date, and a chapter on Textiles and one on Poisons and their Antidotes have been added.

Instructors who use this book will find that an occasional visit, with the class, to some industrial establishment will add greatly to the interest. In almost every community there may be found gas, water, or electric light plants, and ice plants, bakeries, confectionaries, canning factories, creameries, and vinegar factories are common. It is an excellent plan also to visit and report on the heating and ventilating systems in school buildings, churches, large halls, and theaters, and to make tests upon the composition, temperature, and humidity of the air which is supplied.

In the laboratory work the student should be required to write out full descriptions of all the work performed, with conclusions upon the results obtained. This is the only way to make the laboratory work of any permanent value.

The author is indebted to Professor C. C. Young for valuable assistance in preparing this edition.

Lawrence, Kan., April 1, 1917.

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Contents

PAGE

Introduction xxv

Chapter I

History — Proof that air has weight — Experiments of Galileo, Torricelli, and Lavoisier — Experiments by Cavendish and by Bunsen, Leroy, and Regnault — Recent discoveries by Ramsay and Rayleigh — Methods used for detecting argon and helium — Composition of the air — Experiments to illustrate composition of air — Proof that air is a mechanical mixture — Methods used for analysis of air — Oxygen in expired air — Moisture in the atmosphere — Proof that moist air is lighter than ordinary air — Experiments illustrating the presence of moisture in air — Carbon dioxid in free air and in closed rooms — Effect of impure air upon the system — Experiments to show the amount of carbon dioxid in the air — Nitric acid, ammonia, and other impurities in the atmosphere — Hydrogen peroxid — Ozone and its properties — Experiments upon ozone — The effect of carbon monoxid upon the system — Substances in suspension in the air — Methods of studying the dust of the atmosphere — Bacteria in city air — Microorganisms not abundant at great altitudes — Infectious diseases readily propagated by dust — Decrease ix

CONTENTS in tuberculosis — Vacuum cleaners — Experiments to show presence of arsenic in papers and fabrics — Injurious trades — Composition of ground air — Source of the impurities in ground air — Effects of ground air upon the system — Offensive gases . . 1

Chapter II

History — Combustible elements in fuels — How heat is produced by combustion — Cellulose, the basis of ordinary fuels — Wood as fuel — Amount of water in different woods — Effect of drying upon wood — Composition of wood ashes — Charcoal — Method of making charcoal — Peat — Occurrence and preparation — Coal — Characteristics of different kinds of coal — Composition of different coals — The analysis of coals — Briquettes — Petroleum coke — Natural and artificial gases as fuel — Advantages of gas as fuel — Burners used with gas — Composition of natural gas — Gasoline — Kerosene — Wood alcohol — Grain alcohol 26

Chapter III

Common methods of heating — Use and economy of the fireplace — The stove as a heating device — Use of the hot-air furnace — Use of steam with direct and indirect radiation — Advantages of hot- water heating — Electricity as a source of heat — Ventilation

— Why little attention is paid to this subject — Necessity for ventilation — Amount of air used up in respiration — Heat retention a cause of discomfort

— Contamination of air by lights — Properties of impure air — Amount of fresh air necessary to health — Crowd poisoning — Conditions necessary for good

CONTENTS XI

PAGE

ventilation — Mechanical system of ventilation — Devices used for ventilating ordinary rooms — Experiments upon air currents and temperature . . 39

Chapter IV

Sources of artificial light — Solid, liquid, and gaseous light-producing substances — The candle flame — Experiments with the candle flame — Use of gas for illuminating purposes — History of the development of artificial light — Candles as a source of fight — Composition of candles — Method of making candles — Use of kerosene for lighting — Sources of coal oil and method of making — Distillates from Pennsylvania petroleums

— Adulteration of kerosene — Experiments to show the flash point of oils — History of illuminating gas

— Method of making gas — By-products in gas manufacture — Method of making water gas and its properties — Preparation and properties of air gas — Pintsch gas — Blaugas — Calcium carbid and its use in making acetylene — Use of acetylene on automobiles — Composition of illuminating gases — Experiments upon coal gas — Experiments upon acetylene gas — Lamps used for the burning of oils

— Incandescent gas lights — Method of making mantles and their composition — Advantages of incandescent lights — Electric lights — The ideal light

of the future — Table of light efficiencies ... 54

Chapter V

Impurities in water — Source of impurities in water — Character of rain, river, lake, and well waters — Mineral waters — Experiments upon mineral substances in water — Hard waters — Disadvantages of

Xll CONTENTS the use of hard water — Experiments on hard water — Organic impurities in water — Source of these impurities — The sanitary analysis of a water — Meaning of the presence of free ammonia, albuminoid ammonia, nitrates, nitrites, and chlorin in a drinking water — Experiments to determine the quality of water — Analysis of city water supplies — Table — Drinking water and disease — Effect of suspended matter in water — Organic impurities in water — Illustration from the city of Messina — Illustration from the Valley of the Tees, England — Illustration from Plymouth, Pennsylvania — Illustration from Hamburg, Germany — Illustration from Lausen, Switzerland — Danger from sewage pollution — The cause of pollution of ordinary wells . . ■ .71

CHAPTER VI Purification of Water Supplies

Natural purification — Processes used — Methods of purification — Coagulation and sedimentation — History — Artificial purification — Slow sand filtration — Construction of filters — Cleaning the filter

— Rapid sand or mechanical filtration — Method of operation — Water softening — Reactions involved

— Disinfection of water supplies — Use of hypochlorite of lime — Use of liquid chlorin — Use of ultra-violet light — Household purification of water

— Domestic filters — Boiling the water — Use of ozone and of ultra-violet fight for household purification — Effect of freezing — Water supplies of cities

— Per capita amount supplied — Surface waters collected in impounding reservoirs — Water supplied by small lakes — Water supplied from the Great Lakes — Water supplied from rivers — Cities of United States supplied from rivers — Ground water supply — Cities supplied in this way — Disadvantages of ground water — Storage of ground water. 90

CONTENTS Xlll

CHAPTER VII Sewage : Disposal of Household Waste and Garbage

PAGE

Composition of sewage — Oxidation of sewage — Modern theories for purification of sewage — Disposal of sewage by dilution — The sewage of Milwaukee and Chicago — Disposal of sewage by irrigation — Intermittent filtration — The septic tank — The Imhof tank — The activated sludge process — Disinfection of sewage — Precipitation of sewage — Disposal of household waste — The use of the stove or furnace for disposal of waste — Burying in the soil

— Methods used for disposing of waste in large cities

— Cremation as used abroad — ''Reduction" of garbage and utilization as a fertilizer — Municipal refuse 103

CHAPTER VIII Textiles

Materials used — Origin of materials — Cotton fibers — Structure — Mercerized cotton — Flax (linen) — Method of treating to obtain fiber — Structure — Wool — Description of wool fibers — Wool grease

— Scouring wool — Silk — How produced — Description of silk — Artificial silk — Pyroxylin silk — Cuprammonium silk — Viscose process — Reactions of fibers with alkalies and with acids — Differentiation between various textiles — Fire-proofing cotton

— References 114

CHAPTER IX Cleaning: Soap, Bluing, and Bleaching

Necessity for cleanliness — Cleaning materials act mechanically or chemically — Polishing powder — Borax

— Ammonia — Cleaning leather, wood, etc. — Solvents for grease — Cleaning marble — Use of solvents upon household fabrics — Removal of grease by blotting paper, French chalk, fuller's earth — Treat-

XIV CONTENTS ment of paint spots with oil and turpentine — Sugar and acid spots — Ink spots — To clean tarnished silver — Cleaning polished brass and copper — Experiment to remove iron rust 123

Soap : History of the discovery of soap — Raw material used in its manufacture — Process of saponification

— Method of making soap commercially — Mottled, toilet, transparent, and perfumed soaps — Scouring soaps and their use — Soft soap — No economy in the use of a cheap soap — Advantage of a well-dried soap — Theories in regard to the action of soap — The use of hard water — Experiments upon making soap and in testing its composition — Washing soda

— Experiments to test a washing powder . . 128 Bluing : Use of indigo — Prussian blue for making liquid

blue — Ultramarine and its use as a bluing material

— Experiments with Prussian blue and with ultramarine — Aniline colors as used in liquid blues . . 136

Bleaching : Use of bleaching agents — Calcium hypochlorite — Hydrogen peroxid — Sulfur dioxid . . 138

CHAPTER X Disinfectants, Antiseptics, and Deodorants

The necessity for using disinfectants and antiseptics — The importance of the sense of smell — Tests for disinfectants — How bacteria multiply — An ideal disinfectant — Use of the following disinfectants and antiseptics : Sunlight — Dry air — Dry earth — Charcoal — Experiments upon the action of animal charcoal — Dry heat and its use — Sulfur dioxid as a disinfectant — Carbolic acid and its value — Copper sulfate — Iron sulfate — Zinc chlorid — Potassium permanganate — Fire, the most effective means of destroying disease germs — Steam as used for destruc-

CONTENTS XV tion of germs — Boiling water and how it may be used — Chlorid of lime, its value and use — Formaldehyde gas and the method of applying it — Corrosive sublimate and its value as an antiseptic . . . 140

Chapter XI

Opportunities for becoming accidentally poisoned — Chronic and acute poisoning — Poisons and corrosives — Treatment when poisoned with alkalies — With acids — Metallic poisons — Symptoms and antidote in case of copper poisoning — Treatment for zinc poisoning — Lead poisoning with method of treatment — Mercury poisoning — Arsenic, description and properties — Treatment — Antimony salts

— Oxalic acid, with method of treatment in case of poisoning — Hydrocyanic acid — Phosphorus poisoning — Morphine poisoning — Strychnine — Aconite

— Carbolic acid — Wood alcohol — Ptomaine poisoning — Carbon monoxid 152

CHAPTER XII Food

Definition of food — Distinction between food and medicine — Uses of food — Delicacy of the sense of taste — Experience has been our guide in selecting food — Variety of food — Value of a mixed diet — Selecting food suited to habit and employment — Reasons for cooking foods — Food used to build up the tissues

XVi CONTENTS and supply energy — Synthetic foods — Elements contained in the body — Amount of substances occurring in the body — Carbohydrate and nitrogenous foods — The cellulose, cane sugar, and glucose groups — Proximate substances contained in foods, viz. water, fat, carbohydrates, protein, organic acids, and mineral salts 161

CHAPTER XIII Cellulose, Starch, Dextrin, Legumes

Occurrence of cellulose and its properties — Experiments upon cellulose — Sources of starch and amount found in various cereals — Wheat, its composition — Comparison of different grades of wheat — The composition and properties of wheat flour — Analysis of different kinds of flour — Milling products of flour

— Corn — Composition, properties, and uses — Comparison of wheat and corn — Oats — Composition and peculiar characteristics — Rye — Its source, composition, and use — Barley — Its composition — Rice

— Its cultivation, composition, and properties — Potatoes — History of the introduction of potatoes

— Composition and value of potatoes — This tuber not suited for use as a staple article of diet — Composition of sweet potatoes — Cassava (tapioca) — Its source and method of manufacture — The source and method of preparing arrowroot — Properties of other starches, sago, tous les mois, etc. — Adulteration of starch and method used for the detection of adulteration — Legumes — Cultivation of the members of the Pulse Family — Properties of the legumes — Composition of peas, beans, and lentils — Experiments upon legumes — Value of legumes as a food — Bananas — Starch — Sources of commercial starch and method for making — Experiments upon starch

CONTENTS XV11

— Dextrin and method of making — Gums — Inulin

— Physical properties of starch — Experiments with starch grains — Chemical properties of starch — Experiments in making starch and to show its properties — Experiments upon dextrose — Experiments with diastase 170

Chapter XIV

Primitive method of making bread — Two general methods of making dough light — First, non-fermentation method ; second, fermentation method — Bread not raised with fermentation : by the use of eggs, alcoholic liquors, ammonium carbonate, baking soda, baking soda and molasses, carbon dioxid, baking soda and hydrochloric acid, baking soda and sour milk, baking soda and cream of tartar — Baking powders — Cream-of-tartar powders — Phosphate powders — Alum powders — Experiments with baking powders — Bread raised by fermentation : first, by use of yeast ; second, by use of leaven; third, by the salt-rising process — Composition and properties of yeast — Method of making yeast — Theory of use of leaven

— What takes place in the salt-rising process — Chemistry of the fermentation of dough — Essentials to be noted in making good bread — Construction and use of the oven — Temperature used in baking

— Difference between fresh and stale bread — Amount of bread that can be made from a given weight of flour — Composition of different kinds of bread — Difference between the crumb and crust — Starch alone will not sustain life — Value of a mixed diet to man — Bread a nutritious food — Value of white vs. whole-wheat bread — Patent flour —

XV1U CONTENTS

Stale bread and why it is wholesome — Corn bread

— Why some bread is bad — Adulteration of flour and bread — Use of copper sulfate to make bread white — Use of alum as an adulterant — Experiments upon copper sulfate in bread — Experiments

to detect alum — Occurrence of ergot in flour . . 201

CHAPTER XV Breakfast Foods and Other Special Foods

Foods for infants and invalids — Breakfast foods and their composition — Conclusion in regard to the use of breakfast foods — Macaroni, vermicelli, etc., as foods

— Composition of macaroni . . . . 229

Chapter XVI

History and classification — Consumption of sugar in different countries — Different sugars known to the chemist — Classification of sugars — The sucrose and glucose groups — Members of the sucrose group — Sources of cane sugar — The sugar cane as a source of sugar — Cultivating the sugar cane — Extraction of the juice — Purification of the juice by the use of sulfurous acid — Concentration of the juice in the " triple effect" and in the vacuum pan — Use of the centrifugal — Treatment of the sirup — Making sugar from the sugar beet — History of the development of the industry — Use of the diffusion process — Concentration and purification of the juice — Manufacture of maple sugar — Adulteration of maple sugar

— Sorghum sugar and its manufacture — Molasses

— Sugar-refining — Methods adopted in the commercial centers — Use of the bone-black filter — Revivifying bone black — Use of the vacuum pan and centrifugal — Granulated sugar — Powdered and cube sugar — Experiments to show the properties of

CONTENTS XIX

PAGE

sugar — Composition of raw and of refined sugars

— Food value of sugars — Maltose, its source and properties — Lactose, method of making and properties 235

CHAPTER XVII Glucose or Grape-sugar Group

Processes used for the manufacture of glucose and its composition — Uses of glucose — Healthfulness of the product — Experiments upon glucose — Invert sugars — Levulose — Honey — Composition and properties of honey — Experiments with honey . 251

CHAPTER XVIII Leaves, Stalks, Roots, etc., used as Food

Value of this class of nutrients — Carrots, parsnips — Turnips and beets — Leaves as food — Composition and value of cabbage — Greens — Asparagus — Rhubarb, etc 257

The use of onions and leeks — Tomatoes and their use — Irish moss and its composition — Mushrooms and toadstools — The growing of mushrooms and their composition — The selection of the non-poisonous varieties 260

CHAPTER XIX Composition and Food Value of Fruits

Some definitions — Composition of fruit at different periods of growth — Change in composition as illustrated by analysis of apples — The ripening of fruit

— Table showing composition of various fruits — Value and properties of the different ingredients in fruits — Malic acid, citric acid, tartaric acid with experiments — Effect of cooking upon fruits . . 263

XX CONTENTS

Jams and jellies and their adulteration — Opportunity for falsification in this material — Substitutes for jam and jelly upon the market — Experiments upon adulterated jellies — Fruit sirups — Flavoring extracts . 270

CHAPTER XX Edible Fats and Oils — Food Value of Nuts

Composition of edible fats — Digestion of fats and oils — Amount of fat in different vegetable and animal substances — Use of cottonseed oil in cooking — Use of oil of cocoanut — Lard — Method of making the different grades, such as refined lard, kettle-rendered lard, neutral lard — Adulteration of lard — Manufacture of compound lard, cottolene, cottosuet — Use of nuts as food — Composition of the more important nuts — Removal of excess of oil from some varieties — Value of almonds for food — Use of peanuts as food 274

CHAPTER XXI Meat

Concentration of nitrogenous food by animals — Importance of nitrogen in the animal body — Classification of nitrogenous bodies — Functions of albuminous substances — Structure of lean meat — Constituents of meat — Composition of beef — Use of animal food in different countries — Cooking of meat by roasting, broiling, etc. — Beef extracts and their value — Different kinds of meat similar in composition — Fish as a cheap and nutritious food — Characteristics of this food — Fat and lean fish — Use and food value of oysters — Danger from trichina, tapeworms, etc., in pork — Experiments upon cooking meat . . . 280

CONTENTS XXI

CHAPTER XXII Eggs

PAGE

Composition of egg white and egg yolk — Use of eggs as food — Methods of preservation — Desiccated eggs

— Proper method for cooking eggs — Experiments with egg white and egg yolk 291

CHAPTER XXIII Milk, Cheese, and Butter

Composition of milk of different animals — Composition of various kinds of milk — Experiments upon the specific gravity of milk — Composition of butter fat and method for its determination — Use of koumiss

— Experiments to determine amount of butter fat and total solids — Cause of the souring of milk — Experiments with coagulants — Methods of raising cream — Sterilized and pasteurized milk — Condensed milk — Its composition — Nature of modified milk and how it is prepared — Experiments to detect milk adulteration — Cheese — The methods for its manufacture — Description of different kinds of cheese — Table showing composition of various cheeses — Butter and butter substitutes — Conditions necessary for making good butter — Renovated or process butter

— Manufacture of oleomargarin — Materials used in making oleomargarin — Attitude of the government toward this industry — Experiments with butter . 295

Chapter XXIV

General demand for beverages of this class — Amount of tea, coffee, and cocoa used in the United States — Source of tea — Composition of green and black tea

XX11 CONTENTS

— The most important constituents and their properties — Experiments upon making a decoction of tea and its properties — Paraguay tea — Coffee-leaf tea — Coffee — History of its growth — Method of cultivation and preparation of the berry — Analysis of coffee — Effect of roasting — Adulteration of ground coffee — How to make the beverage — Coffee substitutes — Cocoa and chocolate — History of this product — Method of growing the nuts — Composition of chocolate, cocoa, cocoa shells — Value of cocoa as a food material — Manufacture of chocolate — Experiments upon chocolate — The cola nut

— Comparison of the effect of the non-intoxicating beverages upon the system 312

Chapter XXV

Use of alcohol from the earliest history of the world — Properties of alcohol — Consumption of alcoholic liquors in different countries — Classification of alcoholic beverages into fermented, malt, distilled liquors, and cordials — Per cent of sugar in different fruits — Wine — Source of wine — Method of making

— Fermentation — Aging wine — Chemical reaction involved in wine making — Changes produced by aging — Composition of various wines — Classification of wines — Why grapes make better wines than other fruits — Adulteration and plastering of wines

— Diseases of wines — Experiments upon wine — Cider — Method of making — Adulteration and falsification — Beer — Method of making malt — Chemical changes involved in manufacture of beer — Composition of some malted liquors — Experiments upon beer — Distilled liquors — Definition — Method of making alcohol — Distinction between brandy, whisky, rum, and gin — Adulteration of fermented liquors — Liqueurs — Cordials — Physiological action of alcohol 327

CONTENTS XX111

CHAPTER XXVI Food Accessories

PAGE

Difference between condiments and spices — Common adulterants of ground spices — Source and properties of cloves, cinnamon, pepper, ginger, nutmeg, mustard

— Experiments upon spices — Vinegar — Chemical changes involved in its manufacture — Material used, such as wine, fruit, spirits, malt, etc. — Quick vinegar process — Experiments upon vinegar — Salt — Occurrence of salt in different parts of the world — Method of obtaining the commercial salt — Composition of average samples — Uses of salt . . . 345

CHAPTER XXVII Preservation of Foods — Coloring of Food Products

Method of preservation of food formerly adopted and those in use at present time — Conditions favoring fermentation and decay — Preservation by canning — Canning as carried on in large manufactories — Experiments upon preservation of food — Use of tin cans

— Experiments upon the composition of the can — Recent use of chemical preservatives — Objection to the use of these substances — Use and method for detection of borax, sodium benzoate, salicylic acid, sodium sulfite, and formaldehyde — Coloring of food products — Objections to this custom — Use of copper to give a green color to pickles — Experiments upon food coloring 354

CHAPTER XXVIII Economy in the Selection and Preparation of Food — Dietaries

Proper methods for cooking food — How starch is affected by heat — Changes which fats undergo in cooking and

XXIV CONTENTS the effect of heat upon them — Leguminous foods and how they should be cooked — A large amount of nutriment at small cost — Comparison of vegetable and animal foods — Relation between cost of the food and its nutritive value — Importance of cooking each food in the best way — The use of a steam cooker in economizing fuel — The Aladdin oven as an economic kitchen utensil — The fireless cooker . . . 365 Dietaries : History of the study of the composition of food — Experiments carried on by the United States government — Definition of calories — Fuel value of different classes of nutrients — Use of the respiration calorimeter — A study of the food of different individuals or classes — Table showing dietaries used in the United States and abroad — Standard dietaries as estimated by different authorities — The use of smaller amounts of proteids than the accepted dietary would indicate — The ideal ration — Cost of food and nutritive ratio — Per cent of income expended for food by people of different classes ..... 370

Introduction

A knowledge of the science of chemistry is necessary for a proper understanding of so many of the other sciences that it is not strange that this subject is so often required of students in the lower grades. To know even the rudiments of physics, botany, biology, geology, mineralogy, or physiology, the student must have a fair knowledge of chemistry.

When we consider, however, the arts that have to do with modern living, — the eating, drinking, and breathing, all of which may be prosaic enough in their way, — it is evident that the foundation study here also is a knowledge of the composition of the substances surrounding us.

A knowledge of the relations to health of pure air, unpolluted water, and wholesome food will have much to do with improvement in sanitary conditions, not only of students themselves, but, through them, of the people at large. The air is usually said to be free, but pure air and sunshine cost money, as the crowded tenements show. The best lighted and ventilated rooms are worth the most. Since physicians agree that impure air is a predisposing cause of a large per cent of diseases, it is of the greatest importance that a knowledge of the

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XXVI INTRODUCTION

danger from this source be diffused among all classes of people.

Water is furnished by the well or cistern at the farm or the isolated country house, and for a very large population by a corporation or by the municipality itself. Those who use the water from the private source of supply or those who furnish it to the multitude of the city, should know how water becomes polluted and how to guard against disease from this source.

The food supply is obtained from various sources. There is a growing tendency to have food prepared outside the household, and the family learn to depend on the baker, the grocer, and the packing house for their food. With this tendency comes the temptation to those who furnish food ready prepared or dressed, to falsify or adulterate it. because they have the opportunity.